How Things Work 3-minute video · ages 4-8 · free coloring page
Why do things glow under a black light?
Whoa, my socks are glowing! Why do things glow under a black light?
3 min
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Free coloring page
The scene from the video as a coloring page, plus the three-sentence answer, the experiment, and a QR code back to this page. One sheet, US Letter, black and white.
The answer in three parts
Why?
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Some light is invisible.
Just past violet, there is a light called ultraviolet, or U V for short. Your eyes can't see it. A black light is a lamp that gives off mostly ultraviolet light.
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Electrons jump up...
Some things are full of special stuff that soaks up ultraviolet light. When the invisible light hits them, their electrons get energy and jump up high. Boing!
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...and fall back down with light.
Then they fall back down and let the energy go as light that we can see, like bright blue, green or pink. Invisible light goes in, and colorful light comes out!
For grown-ups: Never stare right into a black light. In a glow stick, a chemical reaction gives the electrons their energy; under a black light, the invisible light does it, and the glow stops right away when the light turns off.
What glows?
- White socksfrom laundry soap
- Highlighter inkshines bright
- Teethglow a little
- Tonic waterglows blue
- Some rocksin amazing colors
A tiny experiment
Try it!
Glow hunt
You need: a black light flashlight, a highlighter and a grown-up
- Draw with a highlighter.
- Turn off the lights, and shine the black light on your drawing.
- Then try white paper and a white sock. What glows?
What happened? Invisible light goes in, and colorful light comes out!
Did you know?
Many laundry soaps leave a special glowing stuff on clothes, to make white look extra white. Under a black light, it shines bright blue!
Glow-in-the-dark stars soak up light and keep glowing after the light goes off, because their electrons take their time coming back down.
Your guide in this video
I'm Zippy, the tiny electron. Invisible light goes in, and colorful light comes out!
Zippy is a tiny round blue electron with a yellow spark on top. Electrons like Zippy zoom around everything, even your hair!
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